1. Field of the Invention
The present invention relates to a piezoelectric transformer device, a housing for the piezoelectric transformer, and a method of manufacturing them, and more particularly to a piezoelectric transformer device, a housing for the piezoelectric transformer, and a method of manufacturing them, in which the housing has integral lead frames resiliently protruded to contact input and output portions of the piezoelectric element, and is comprised of a pair of housing parts surrounding both sides of the piezoelectric transformer, and the lead frames are outwardly extended from the housing.
2. Description of the Prior Art
In general, piezoelectric transformers are widely used these days because the piezoelectric transformer can be reduced in its size and thickness as compared with a coil type transformer, and is characterized by high efficiency and insulation performance and incombustibility. Such piezoelectric transformers are used with inverters for back-lights of color liquid crystal displays and high voltage generating circuits. At the moment, products in which a back-light inverter of a color liquid crystal display is incorporated include notebooks, PDAs (Personal Digital Assistants), DVCs (Digital Video Cameras), DSCs (Digital Still Cameras), and high voltage generating circuits are used in dust collectors, air purifiers and ozone generators.
A construction and operating principles of a piezoelectric transformer will be described as follows. In the piezoelectric transformer which is known as a DC high voltage generating circuit, when a driving portion of the piezoelectric transformer is applied with its inherent resonant frequency, high voltage is induced at a vibrating portion by its piezoelectric effect. Although piezoelectric transformers can be classified into various kinds of piezoelectric transformers, a Rosenberg type piezoelectric transformer, which employs longitudinal vibration of a rectangular piezoelectric ceramic, is generally used.
FIG. 1 shows a construction of the Rosenberg type piezoelectric transformer. As shown in the drawing, an input portion 120 is symmetrically provided at its upper and lower surfaces with electrode faces 110, and an output portion 130 is provided at its end surface with electrode faces 140. The input portion 120 having the input electrodes 110 is polarized in the thickness (T) direction, and the output portion 130 having the output electrode is polarized in the lengthwise (L) direction. When the input electrode is applied with AC voltage corresponding to resonant frequency of the piezoelectric element, voltage is generated from the output electrode by piezoelectric effect and thus electric power is supplied to a load. That is, AC voltage applied to the input portion is converted to higher voltage at the output portion via ultrasonic mechanical vibration, thereby increasing voltage.
As illustrated in the above, a piezoelectric transformer comprises the input portion 120 and the output portion 130. The input portion serves as a driving portion for converting input electrical energy into mechanical vibration energy, and includes input electrodes at its upper and lower surfaces. The output portion serves as a generating portion for converting the mechanical vibration energy into electrical energy, and includes the output electrode at its right end surface. When the input portion is applied with electric voltage, the input portion is mechanically vibrated. The mechanical vibration is transmitted to the output portion in the lengthwise direction and thus piezoelectric effect occurs due to the mechanical vibration, thereby generating electric voltage. A ratio of input voltage to output voltage is determined by shapes of input portion and output portion of a piezoelectric transformer.
FIG. 2 shows a shape and electrode patterns of a single plate type xcex mode piezoelectric transformer. As shown in the drawing, an input portion of the piezoelectric transformer is printed with input electrodes 210 at its upper and lower surface, and an output portion of the piezoelectric transformer is provided at its end with a xe2x80x9cUxe2x80x9d-shaped output electrode 220.
A conventional housing for accommodating such a piezoelectric transformer is illustrated in FIGS. 3 and 4. A piezoelectric transformer and a housing shown in FIGS. 3 and 4 are disclosed in Japanese Patent Laid-Open No. 8-32135. Solder wires 305 and 306 are connected to the center of node supporting points of an input portion and an output portion of the xcex mode piezoelectric transformer 301 and then connected to a plastic housing 307. The housing is provided with holding protrusions 308 at 4 positions, which are intended to hold the solder wires 305 and 306 extended from the input portion and the output portion. The piezoelectric transformer 301 is applied with adhesive and then attached in the housing 307.
Such a housing for a conventional piezoelectric transformer has a simple construction. However, since both electrode portions of a piezoelectric transformer are soldered with solder wires 305 and 306 and the piezoelectric transformer is mounted on a PCB 310, mass production and quality improvement are difficult due to connection of wires and manufacturing cost is increased due to breakage of wires and an increased number of procedures.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a contact structure of a piezoelectric transformer and a housing in which lead frames are integrally formed with the housing to allow the lead frames to easily contact the piezoelectric transformer and to prevent breakage of the contact.
Another object of the present invention is to provide a housing, which has lead frames, adapted to resiliently support a piezoelectric transformer to improve structural stability and operational effect.
In order to accomplish the above object, the present invention provides a housing for receiving a piezoelectric transformer having a voltage input portion and a voltage output portion, both of which include a plurality of electrodes, including an upper housing part having at least two first lead frames which are protruded at ends thereof to resiliently come into contact with a point of the input portion and a point of the output portion of an upper surface of the piezoelectric transformer. Furthermore, the housing includes a lower housing part having at least two second lead frames which are protruded at ends thereof to resiliently come into contact with a point of the input portion and a point of the output portion of a lower surface of the piezoelectric transformer. The first and second lead frames are outwardly extended from the upper and lower housing parts, and the piezoelectric transformer is received in the upper and lower housing parts such that the piezoelectric transformer is resiliently supported by the first and second lead frames.
According to another embodiment, the present invention provides a housing for receiving a piezoelectric transformer having upper and lower surfaces and side surfaces connecting the upper and lower surfaces, and having a voltage input portion and a voltage output portion, both of which include a plurality of electrodes, including an upper housing part surrounding the upper surface and the side surfaces of the piezoelectric transformer, and having I) at least two first openings formed thereon, and II) at least two first lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the first opening of the upper housing part and is protruded at the extended end to be in contact with at least one electrode of the piezoelectric transformer. Furthermore, the housing includes a lower housing part surrounding the lower surface and the side surfaces of the piezoelectric transformer, and having i) at least two second openings formed thereon, and ii) at least two second lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the second opening of the lower housing part and is protruded at the extended end to be in contact with at least one electrode of the piezoelectric transformer.
According to a further embodiment, the present invention provides a housing for receiving a piezoelectric transformer having upper and lower surfaces and side surfaces connecting the upper and lower surfaces, and having a voltage input portion and a voltage output portion at side surfaces thereof, both of which include a plurality of electrodes, including a first housing part surrounding one of the side surfaces of the piezoelectric transformer on which the electrodes are formed, and having I) at least two first openings formed thereon which are positioned at locations corresponding to the electrodes of the piezoelectric transformer, and II) at least two first lead frames made of conductive elastic material, each of which is extended from a side surface into the inside of the first opening of the upper housing part and is protruded at the extended end to be in contact with at least one electrode of the piezoelectric transformer. Furthermore, the housing includes a second housing part surrounding the other of the side surfaces of the piezoelectric transformer on which the electrodes are formed, and having i) at least two second openings formed thereon which are positioned at locations corresponding to the electrodes of the piezoelectric transformer, and ii) at least two second lead frames made of conductive elastic material, each of which is extended from a side surface into the inside of the second opening of the lower housing part and is protruded at the extended end to be in contact with at least one electrode of the piezoelectric transformer. In addition, the housing includes a clip fitted on the center portion of the first housing part and the center portion of the second housing part to couple the first and second housing parts to each other.
The present invention provides a method of manufacturing a housing for receiving a piezoelectric transformer having a voltage input portion and a voltage output portion, comprising the steps of: preparing a pair of lead frames comprised of rectangular ring-shaped frames, each of which is cut away at one side, the cut ends of the lead frames being protruded laterally to come into contact with input and output contact points of the piezoelectric transformer; providing a pair of housing parts, for receiving the piezoelectric transformer, on the cut ends of the lead frames by carrying out an injection molding on the cut ends of the lead frames and forming openings at the housing parts such that the cut ends of the lead frames are protruded therethrough to resiliently support the piezoelectric transformer; removing lead frames outwardly extended from the pair of housing parts except lead end portions of the lead frames; and bending the lead ends toward a surface of the housing parts to contact the surface, thereby allowing the housing parts to be mounted on a PCB.
In addition, the present invention provides a piezoelectric transformer device comprising: a piezoelectric transformer having rectangular upper and lower surfaces and side surfaces connecting the upper and lower surfaces, and having an input portion formed at upper and lower surfaces of one half part of two half parts of the piezoelectric transformer which are longitudinally and equally divided and an output portion formed at parts of side surfaces and an upper surface adjacent to the side surfaces of the other half part of the piezoelectric transformer; an upper housing part surrounding the upper surface and the side surfaces of the piezoelectric transformer, and having I) at least two first openings formed thereon to expose parts of the input and output portions, and II) at least two first lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the first opening of the upper housing part and is protruded at the extended end to be in contact with the input and output portions of the piezoelectric transformer; and a lower housing part surrounding the lower surface and the side surfaces of the piezoelectric transformer, and having i) at least two second openings formed thereon to expose parts of the input portion and the piezoelectric transformer, and ii) at least two second lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the second opening of the lower housing part and is protruded at the extended end to be in contact with a portion adjacent to the output portion of the piezoelectric transformer.
The present invention also provides a piezoelectric transformer device comprising: a piezoelectric transformer having rectangular upper and lower surfaces and side surfaces connecting the upper and lower surfaces, and having an input portion formed at upper and lower surfaces and side surfaces of a middle portion of the piezoelectric transformer and an output portion formed at upper and lower surfaces and side surfaces of one end of the piezoelectric transformer; an upper housing part surrounding the upper surface and the side surfaces of the piezoelectric transformer, and having I) at least two first openings formed thereon to expose parts of the input and output portions, and II) at least two first lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the first opening of the upper housing part and is protruded at the extended end to be in contact with the input and output portions of the piezoelectric transformer; and a lower housing part surrounding the lower surface and the side surfaces of the piezoelectric transformer, and having i) at least two second openings formed thereon to expose parts of the input portion and the piezoelectric transformer, and ii) at least two second lead frames made of conductive elastic material, each of which is extended from one of the side surfaces into the inside of the second opening of the lower housing part and is protruded at the extended end to be in contact with the input and output portions of the piezoelectric transformer.
Furthermore, the present invention provides a piezoelectric transformer device comprising: a piezoelectric transformer having rectangular upper and lower surfaces and side surfaces connecting the upper and lower surfaces, and having an input portion formed at both side surfaces of a middle portion of the piezoelectric transformer and an output portion formed at both side surfaces of one end of the piezoelectric transformer; a first housing part surrounding one side surface of the both side surfaces on which the input and output portions are formed and both end surfaces adjacent to the side surface, and having I) at least two first openings formed thereon to expose parts of the input and output portions, and II) at least two first lead frames made of conductive elastic material, each of which is extended from a side surface into the inside of the first opening of the first housing part and is protruded at the extended end to be in contact with the input and output portions the piezoelectric transformer; a second housing part surrounding the other side surface of the both side surfaces on which the electrodes are formed and both end surfaces adjacent to the side surface, and having i) at least two second openings formed thereon to expose arts of the input and output portions, and ii) second lead frames made of conductive elastic material, each of which is extended from a side surface into the inside of the second opening of the lower housing part and is protruded at the extended end to be in contact with the input and output portions of the piezoelectric transformer; and a clip fitted on the center portion of the first housing part and the center portion of the second housing part to couple the first and second housing parts to each other.